Retrieving tool



1953 I G. w. WALTON EIAL 2,833,353

- RETRIEVING TOOL Filed June 1, 1954 2 Sheets-Sheet 1 .571 517 [5P5 Graec: W hzuralv .DOAIALfl llJlf C'nerr 5 W21Mg a) v 2,833,353 1 Patented May 6 1958 RETRIEVTNG TOOL George W. Walton, Dallas, Tex., and Donald L. McCarty, Milwaukee, Wis., assignors to Ideco, lnc.

Application June 1, 1954, Serial No. 433,526

7 Claims. (Cl. 166-65) This invention relates to a retrieving tool and more particularly to a permanent magnet type tool which is adapted to magnetically engage and hold paramagnetic objects to permit withdrawal thereof from a drilled bore such as a well bore. Such objects as broken pieces of drill bits and other paramagnetic junk on the inner end of the bore frequently interfere with the drilling operation to such an extent that the removal thereof is imperative before such operation can efliciently proceed.

In most drilling operations it is customary to force a liquid through the drill pipe, a familiar example being the mud so used in the drilling of oil wells. This flow of liquid under pressure may be usefully employed with a magnetic retrieving tool in that fluid discharged under pressure through the tool tends to create'a suspension of objects sought to be removed from the inner end of the bore and that facilitates engagement thereof with the magnet. In various tools heretofore provided forthis purpose, however, the discharge of fluid underpressure from the tool has been through regions of high magnetic density resulting in a decrease in the magnetic efficiency of the tool. In such existing magnetic pick up tools entrance of fluid for return flow through the tool has been at regions of relatively low magnetic density so that the advantageous action of such return flow in moving objects into contact with the tool has been largely wasted.

The present invention overcomes such disadvantages by arranging for discharge of the fluid at a region of low magnetic density as through a coaxial passage in a bipolar bar magnet, and by providing for return flow of the fluid through regions of high magnetic density between said magnet and a spaced surrounding shell. return flow further assists in moving the paramagnetic articles into pockets provided adjacent the inlet passages, which pockets being in regions of high magnetic density attract and hold therein a variety of paramagnetic. objects engaged by the tool. i

It is an important object, therefore, of the present invention to provide a magnetic retrieving tool having fluid discharge and inlet passages therethrough wherein fluid is discharged through the former at a region of low magnetic density and wherein fluid enters the latter at regions of high magnetic density.

It is specifically an important object of this invention to provide fluid discharge and inlet passages so arranged in a retrieving tool of the bi-polar bar magnet type having a surrounding casing.

It is a further object of this invention to provide a magnetic retrieving tool of the kind described wherein pockets are provided between the bar magnet and the casing for the reception of paramagnetic objects carried therein by magnetic attraction and the return flow of fluid.

It is also an object of this invention to provide a magnetic retrieving tool of the kind described which is of simple, durable and relatively inexpensive construction.

Other and further objects of this invention will be ap- Such I parent from the disclosures in the specification and the accompanying drawings.

The invention (in a preferred form) is shown on the drawings and hereinafter more fully described.

' On the drawings:

Fig. 1 is a central vertical section (with parts in elevation) taken through a magnetic retrieving tool embodying the principles of this invention;

Fig. 2 is a section on the line IIII of Fig. l; and

Fig. 3 is a view similar to Fig. 1 showing the tool of this invention with a non-magnetic casing, and Fig. 4 is a section on the line IV-IV of Fig. 3.

As shown on the drawings: 1

In the form of this invention shown in Figs. 1 and 2, the magnetic retrieving tool is carried by a head portion 10'which is adapted to be attached to a string of drill pipe and which is provided with a longitudinal passage 11 through which fluid under pressure may be introduced into the tool. Said passage 11 is provided with an enlarged'shouldered portion 12 and terminates in an extension 13 of lesser diameter than the shouldered portion and extending downwardly therefrom as shown in Fig. 1.

Held tightly against the outer or lower face of the extension 13 of the head portion is a bi-polar bar magnet of unitary construction and formed of an alloy of high magnetic retentivity, such, for example, as the familiar iron, aluminum, cobalt and nickel magnet alloy. The bipolar bar magnet preferably comprises an upper cylindrical section 14a and a lower frusto-conical section 14b, the lower section being made frusto-conical and of lesser diameter at its lower or outer end for a purpose to be described hereinafter. The bi-polar barmagnet isprovided with an axiallongitudinal fluid passage therethrough as shown at 15 and the reduction of the passage in communication with the larger fluid passage 11 through the head fill is provided by a passage plug 16 screwed into an internally threaded portion of the passage 11 through the head adjacent the juncture of the head and the upper end of the oi-polar bar magnet as seen in Fig. 1. v The passage lit and its communicating axial passage 15 through the bi-polar bar magnet form a fluid inlet passage from which fluid is discharged into the end of the bore in a manner to be described hereinafter.

Fluid discharge passages 17 are provided in the extension 13 and shouldered portion 12 in the head .10 to permit of the return flow of fluid into the well bore in a manner which will also be described hereinafter.

Coaxial with the magnet and having its upper end abutcured by welding, is a cylindrical casing 18 preferably made of a high-permeability, low-retentivity paramagnetic material, the lower end of the casing 18 being spaced from the bi -polar bar magnet Ida-14b to a greater extent than the upper end thereof is spaced fromthe portion 14a of said bi-polar bar magnet. By reason of this reduction in magnet area and greater spacing at the lower .end of the magnet and the enclosing cylindrical casing,

maximum flux density is assured at the lower and active end of the retrieving tool. However, it is to be noted that a cylindrical bi-polar magnet with a circulation passage or passages at or near and parallel to its longitudinal axis may be used instead of the magnet l4a-l4b.

If desired, the lower end of the casing 18 may be fitted with a rotary shoe 19 made of the same metal as the casing and having an internally threaded portion engaging external threads of a shouldered portion at the lower end of said casing 18. Tightly engaged against the lower end of the bi-polar bar magnet is a circular pole plate 20 steel. passage 20a which communicates with the passage 15 3 and the bi-polar bar magnet thus completing a fluid inlet passage from the passage 11 in the head 10, through the passage and outwardly through said passage a to discharge fluid under high pressure into a region of relatively low magnetic density.

The outer edge of the pole plate 20 is spaced from the inner face of the cylindrical casing 18 as clearly shown in Fig. 1 and the remainder of the gap between the outer edge of the pole plate and theinner face of the casing 18 is bridged by a spacer member 21 made of non-magnetic material, such, for example, as stainless steel. The spacer member 21 is provided with a plurality of fluid inlet passages 22 which permit of return flow of fluid therethrough upwardly through the space between the casing 18 and the outer face of the magnet'and outwardly through the passages 17 previously described. This means that the return flow of fluid from the end of the bore is through regions of high magnetic density thus tending to move paramagnetic articles into position to be engagedand held at the bottom of t the tool. It will be noted from an examination of Fig. 1, the non-magnetic spacer ring 21 is secured as by welding to the top and to the outer edge of the pole plate 20 and is further secured as by welding to the inner'face of the casing 18.

The pole plate 20 and the non-magnetic ring 21 are welded together, as shown, in Fig. l. The non-magnetic ring 21 is welded to the casing by a weld 23. If desired, the lower face of the extension 13 and the upper face of the pole plate 20 may be slightly depressed to interfit with the respective ends of the bi-polar bar magnet 14a-14b to assist in holding the members in alignment.

It will be further noted that an annular pocket 24 is provided between the inner'wall of the casing 18 and its lower end, the lower surface of the passaged non-magnetic ring 21, and the outer edge of the pole piece 20. This pocket serves to receive and hold small paramagnetic objects which are moved thereinto by the flow of fluid from the end of the bore into the casing and outwardly through the passages 17 and since these pockets are located in a region of high magnetic density, articles so moved thereinto are held firmly therein.

As will be apparentfrom the foregoing, the combination of the extension 13 on the head 10, the casing 18 and the bi-polar bar magnet 14 a'14b provide a magnetic circuit which is of highest reluctance in the regions between the outer edges of the pole plate 20 and the inner face of the casing 18. Thus, the return flow of fluid through the pocket 24 and passages 22 is in a direction to assist the magnetic attraction of a region of greatest magnetic density. Conversely, the flow of fluid through the passages 11, 15 and 20a for discharge into'the end of the bore is through a region of relatively low magnetic density (at the center of the pole of the bar magnet) and. hence such flow of fluid under pressure'through the passage 20a does not materially aifect the magnetic efliciency of of high magnetic density enchances the efficiency of the tool in the picking up of paramagnetic objects.

Fig. 3 of the drawings illustrates another embodiment of the present invention wherein the advantageous outward flow of fluid through a region of low magnetic density and inward flow of fluid through regions of high magnetic densityis attained in a bi-polar magnet type toolhaving a surrounding casing of non-magnetic metal.

The tool shown in Fig. 3 includes a head member 25 which is provided with a longitudinal passage 26 for the introduction therein of fluid under pressure. The passage 26 communicates with a reduced passage 27 which extends to the inner face of the head.

Thehead is provided with a shoulder 28 alfording a stop for the upper end of a'casing to he described-hereinafter. Inside the shoulder 28 the head is provided with a cylindrical portion 29 extending below the shoulder.

.Abutting the inner face of the cylindrical portion 29 :is abutfer or spacer member .30 of aluminum or other non-magnetic material which serves to magnetically insulate from the head a bi-polar bar magnet structure which will now be described. This bi-polar bar magnet structure preferably consists of two bi-polar bar magnets having cylindrical portions 31 and 32 placed in abutting relation with opposite poles in juxtaposition and respectively provided with integral frustoconical portions 31a and 32a, the former of which abuts against the buffer member 30 and the lower of which extends to terminate in a pole shoe or pole plate 33 centrally apertured at 331: and held in position by a spacer ring 34 tilted to the top of the pole plate, as shownin the drawings, and also secured by welding to the inside of the lower end of a casing 36 of non-magnetic material which surrounds the cylindrical portion 29 of the head and is secured to the shoulder 28 by welding, as shown at 37. The casing 36 is coaxially positioned in reference to the magnet assembly 31, 32 and that assembly is held aflixed in its relation to the casing by the affixing of the spacer 34 to the pole plate 33 and and in turn by the aflixing by welding or otherwise of the spacer 34 to the inner wall of the casing 36 near the lower end therww The spacer 34 is provided with a plurality of return fluid passages 35 for a purpose to be described hereinafter.

'Themagnet assembly 31, 32' is provided with an axial longitudinal passage 38 which in turn communicates at its upper end with a passage 38a in the buffer 30, which latter passage communicates with the fluid inlet passage 27 in the head 25. At its lower end the passage 38 communicates with the aperture 33a in the pole plate or pole shoe 33.

Additional fluid discharge passages 39 are provided in the head 25 to permit of the discharge of fluid from the head at points at the upper face of the shoulder 28. The passages 39 register and are in communication with passages 39a extending through the buffer 30.

From the foregoing description it will be apparent that fluid under pressure introduced into the tool through a usual drill pipe (not shown) flows from passage 26 through the passage 27, the aperture 38a in the buffer 30, the passage 38 into the aperture 33a outwardly into the drill'hole from which it is desired to pick up paramagnetic objects. This outward flow of fluid under pressure, as will be obvious, is through a region of low magnetic density so that the magnetic effort of the tool in picking up such objects is not diminished.

The return flow of fluid from the drill hole is inwardly through the passages 35 in the spacer 34 upwardly in the space between the magnet assembly 31, 32 and the casing 36 and outwardly through the apertures 39a and passages 39. This return flow, as will be seen, enters the tool at a region of high] magnetic density so that the magnetic action of the toolis enhanced rather than diminished by such flow of fluid.

An annular pocket 41 is provided between the periphery of the pole plate 33, the underside of the spacer member 34'and the lower end of the inner wall of the casing 36 and this pocket will tend to receive and magnetically hold small paramagnetic objects attracted therein by the magnetic force and sifted in their movement therein by the fluid discharge flow previously described.

The lower end of the casing 36 may be reduced and threaded as shown at 40 for reception of the rotary shoe, as shown in Fig. 1.

As will be noted in this particular embodiment of the instant invention, the return magnetic circuit is through an air path or a path of non-magnetic material. The spacer 34 and the buffer 30, magnetically insulate the magnetic assembly on the head and from the surrounding casing, although such insulation from the latter is not necessary in view of the fact that the surrounding casing 36 is made of non-magnetic metal such as stainless steel.

The frusto-conical portions 31a and 32a of the magnet assembly in reducing the cross-sectional area of the composite bipolar'bar magnet at its the magnetic intensity at those regions.

It will be apparent from the foregoing that this invention provides a tool of great magnetic strength, and

one wherein the magnetic pick-up effort is not diminished by the flow of fluid under pressure from the end of the tool due to the fact that such flow is through a region of low magnetic density. At the same time the magnetic pick up efiort is enhanced by the return flow of fluid into the casing through regions of'high magnetic density.

It will be apparent that by this invention we have provided a simple magnetic retrieving tool making use of a powerful bi-polar' magnet or'bi-polar magnet assembly which is firmly held in position within the enclosing casing and which is so arranged in association with that casing and related fluid passages that the magnetic efliciency of the tool is not decreased by the flow therefrom of fluid under pressure or the return flow of fluid thereinto. Indeed, for reasons above noted, the magnetic pick-up efficiency of the tool is enhanced by this fluid flow arrangement.

We are aware that details of construction may be varied without departing from the principles of this invention and we, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the scope of the appended claims.

We claim as our invention:

1. In a'magnetic retrieving tool, a headed cylindrical casing of magnetic material having a fluid passage through the head thereof, a bi-polar bar magnet inside and spaced from the casing and having an end contacting the inner face of the head inside the casing and having a fluid passage therethrough communicating with the fluid passage in the head and discharging through the end of the magnet remote from the head, an apertured pole plate contacting said last mentioned end of the magnet with the aperture therein aligned with the fluid passage through the magnet, the pole plate projecting beyond the magnet toward the inner wall of the cylindrical casing at the end thereof remote from the head, and a passaged member of non-magnetic material secured to the top of the pole plate adjacent the outer edge thereof and also secured to the inner wall of the cylindrical casing to provide a pocket between said wall of the casing and the outer edge of the pole plate.

2. In a magnetic retrieving tool, a headed cylindrical casing of magnetic material having a fluid inlet passage through the head thereof, a bi-polar bar magnet inside and spaced from the casing and having an end contacting the inner face of the head inside the casing and having a fluid passage therethrough communicating with the fluid passage in the head and discharging through the end of the magnet remote from the head, an apertured pole. plate contacting said last mentioned end of the magnet with the aperture therein aligned with the fluid passage through the magnet, the pole plate projecting beyond the magnet toward the inner wall of the cylindrical casing at the end thereof remote from the head, a passaged member of non-magnetic material secured to the top of the pole plate adjacent the outer edge thereof and also secured to the inner wall of the cylindrical casing to provide a pocket between said wall of the casing and the outer edge of the pole plate, and additional fluid passages formed in the head of the casing outside of the first mentioned fluid passage for 'discharging fluid which enters the casing through said passaged member and flows to said additional passages through the space between the magnet and the casing.

3. In a device of the kind described, a cylindrical casing of non-magnetic material, a passaged head enclosing one end of the casing except for an axial fluid inlet passage therein and fluid outlet passages spaced outwardly from said fluid inlet passage, a passaged buffer of nonmagnetic material abutting the head on the inner side thereof with the passage therethrough registering with poles, likewise increase passages in the head, a bi-polar bar magnet coaxially mounted within the casing and spaced from the walls thereof and having an axial fluid passage .therethrough communicating wlth the fluid passage through the buffer againstwhich an end of the magnet abuts, a pole plate at the other end of the magnet spaced at its periphery from the walls of the casing and having a fluid passage therethrough registering with the last mentioned fluid passage, a spacer member secured to the pole plate and to the inner wall of the casing and having passages therein communicating with the space between the magnet and the casing and thence with the fluid outlet passages in the head to permit the return flow of fluid.

4. In a device of the kind described, a cylindrical casing of non-magnetic material, a passaged head closing one end of the casing except for an axial fluid inlet passage therein and fluid outlet passages therethrough spaced outwardly from said fluid inlet passage, a passaged buffer of non-magnetic material abutting the head inside thereof, with the passage therethrough registering with the fluid inlet passage in the head having additional passages registering with the fluid outlet passages in the head, a bi-polar bar magnet coaxially mounted within the casing and spaced from the walls thereof and having an axial fluid passage therethrough communicating with the fluid passage through the buffer against which an end of the magnet abuts, a pole plate at the other end of the magnet spaced at its periphery from the walls of the casing and having a fluid passage therethrough registering with the last mentioned fluid passage, a spacer member secured to the top of the pole plate and to the inner wall of the casing to provide pockets defined by theperimeter of the .pole plate, the outer surface of the spacer and the inner wall of the casing outside the spacer, said spacer having passages therethrough communicating with the space between the magnet and the casing and thence with the fluid passages in the head to permit return flow of fluid.

5. In a device of the kind described, a cylindrical casing of non-magnetic material, a passaged head closing one end of the casing except for an axial fluid inlet passage therein and fluid outlet passages therein spaced outwardly from said fluid inlet passage, a passaged buffer of non-magnetic material abutting the head inside thereof with the passage therethrough registering with the fluid inlet passage in the head having additional passages registering with the fluid outlet passages in the head, a plurality of bi-polar bar magnets abutting at opposite poles, coaxially aligned and spaced from the walls of the casing mounted within the casing and having registered axial fluid passages therethrough communicating with the fluid passage through the buffer against which an end of the endmost' magnet abuts, a pole plate at the outer end of the other .endmost magnet spaced at its periphery from the walls of the casing and having a fluid passage therethrough registering with the last mentioned fluid passage, a spacer member secured to the pole plate and to the inner wall of the casing and having passages therein communicating with the space between the magnet and the casing and thence with the fluid outlet passages in the head to permit return flow of fluid.

6. In a magnetic retrieving tool for well bores, a downwardly extending bar magnet having one pole at the bottom thereof defining a first zone of minimum flux density at the central portion of the bottom and a second zone of maximum flux density around the periphery of the bottom, a head member carrying the magnet and having a central passageway therein adapted to receive fluid from a drill pipe, said magnet having a centrally aligned aperture communicating with said central passageway and opening into said first zone for flowing fluid downwardly past said magnet, and means carried by the head member defining a second passageway in said second zone for return of fluid upwardly past said magnet.

7. .In a magnetic retrieving tool for Well bores, a downwardly extending bar, magnet having one pole at the density at the central portion of the bottomand a second zone of maximumlflux density around the periphery of the bottom, a head member carrying the magnet and having a central passageway. therein adapted to receive fluid from a drill pipe, said magnet having a centrally 7 8 7 said second zone for return of fluid upwardly past said magnet. i

References fiited in the file of this patent UNITED STATES PATENTS 2,431,361 Athy Nov. 25, 1947 2,556,849 Nalley et a1. June 12, 1951 2,595,632 'Bivings et al. .-May 6, 1952 2,657,752 Ballew et, a1. Nov. 3, 1953 2,6 68,'077 Kirby Feb. 2, 1954 FOREIGN PATENTS France Oct. 28, 1953 

